Electric clock ratchet drive



April 10, 1956 R. H. SULLIVAN ETAL ELECTRIC CLOCK RATCHET DRIVE OriginalFiled July 11, 1945 3 Sheets-Sheet 1 INVENTOR. Peter R. Canton? 8 ByRaymond H. Sullivan Attorney April 10, 1956 R. H. SULLIVAN ET ALELECTRIC CLOCK RATCHET DRIVE Original Filed July 11, 1945 3 Sheets-Sheet2 Fig. 3

Fig. 5

INVENTOR. Peter R. Comm 8; y Raymond H. Sullivan Attorney April 10, 1956R. H. SULLIVAN EI'AL ELECTRIC CLOCK RATCHET DRIVE Original Filed July11, 1945 Fig. 8

I62 (H (H I64 3 Sheets-Sheet 3 IN V EN TOR.

Pefer R. Content 8 By Raymond H. Sullivan AHorney United States PatentELECTRIC CLOCK RATCHET DRIVE Raymond H. Sullivan and Peter R. Contant,Rochester,

N. Y., assignors to General Motors Corporation, Detrait, Mich., acorporation of Delaware Original application July 11, 1945, Serial No.604,386,

now Patent No. 2,631,423, dated March 17, 1953. "Divided and thisapplication January 23, 1953, Serial No. 336,366

3 Claims. (Cl. 58-28) The present invention relates generally toelectricclocks and more particularly to certain improvements in a clockof the electromagnetic impulse type adapted especially The principalobject of the invention is to provide a clock of this type of relativelysimple constructional design, small overall dimensions and lowmanufacturing cost which will give long and reliable service under suchvariable voltage, temperature and vibration conditions as areencountered in automobile-use.

One feature of the present construction involves the use of a singleelectromagnet with poles associated with a timing mechanism including abalance wheel armature which controls and is sustained in oscillationbyintermib tent energization of the electromagnet, and with furtherpoles associated with a separate driving mechanism including an armatureto drive the clock gear train.

A further feature comprises the provision of means to compensate forvariations in voltage and regulate the strength of the magnetic field inthe balance wheel circuit and a means to prevent destructive sparking atthe contact points of the timing mechanism.

Many other features of the present invention including provisions forstarting and the construction and relative arrangement of the severalparts of the clock will be apparent from or specifically noted in thedescription of the embodiment shown in the accompanying drawings.

In the drawings:

Fig. l is a perspective view of the clock mechanism.

Fig. 2 is a bottom plan view of the clock with the back coverand otherparts removed or broken away.

'Fig. 3 is a transverse section with parts in elevation.

Fig. 4 is an enlarged fragmentary section of thedriving mechanism takensubstantially on line 4-4 of Fig. 2.

Fig. 5 is a fragmentary elevation of part of the driving mechanism ofFig. 4.

Fig. 6 is a fragmentary front view taken substantially on line'66 ofFig. 3.

' Fig. 7 is a fragmentary section taken substantially on line 77 of Fig.6.

Fig. 8 is a diagrammatic view showing the electrical starting andrunning circuits.

Referring first to Figs. 1 to 3, a base plate 10 is provided with spacedpillars 12 and 14 on which abridge 16 is secured by screws 18. Athree-pole armature '20 which also functions as the balance wheel ismounted on astatf 22 journaled in jeweled bearings 24 in the bridge 16-and an ofiset portion of base plate 10. A .hairspring- 26 is secured atits inner end to collet 28 on the staff 22 and is secured at its outerend to a post 30 on the base plate with the outer turn of the hairspringpassing through a slot in a regulator arm 32. This arm is connected asshown in Figs 3 to an operating indicator pointer .34 by a pivot post 36extending through and rotatablein a bearingplate 38 on base plate 10below the staff 2210 provide for the adjustment of the arm 32 to shortenor lengthen "ice the effective length of the hairspring to regulate theperiod of oscillation of'the balance wheel in the usual manner.

An electrical contact 49 which may consist of a small pin or rodextending parallel to the staff 22 is secured electrical contact blade56 is secured to the end of the spring portion 48 and is so located asto project into the arcuate path of movement of the contact 40 onoscillation of the armature 20. The coils of the helicalspring 46 aretightly wound together to effect a rapid damping of'the vibrations ofthe contact blade 50 when the blade is released after the deflectionthereof by the contact 40 as it engages and moves past the blade duringoscillation of the armature 20.

During normal operation the contact 40 alternately engages the oppositefaces of the contact blade 50 to pro- .vide for the intermittentenergization of the winding of an electromagnet, indicated generally at52, which .is adapted to impart periodic impulses to the armature 20 tomaintain the oscillation thereof. The electromagnet includes a core 54having one end secured to the base plate 10 and upper and lower polepieces 56.and 58, respectively, which are so formed as to locate thepole tips in the plane of the armature 26 at points relatively 'close tothe periphery thereof.

The balance wheel armature assembly and the electromagnet with its polepieces 56 and 58 and the contact arrangement above described constitutea timing mechanism in which the balance wheel armature operates withoutrestraint other than that imposed by the hairspring, the pivot friction,and the mechanical load imposed by the operation of the contacts. Sincethis mechanical load and the pivot friction is quite low and not subjectto any appreciable variations, it will be seen that the balance wheelarmature oscillates at a frequency determined principally'by its massand the torque of the hairspring.

"Referring now to the driving mechanism for the clock gear train, theelectromagnet 52 is provided with additional upper and lower pole pieces60 and 62, respectively, which extend parallel to one another andtermimate in vertically spaced ends adaptedto impart periodic impulsesto an armature 64 which is pivotally mounted for limited oscillationbetween the ends of the pole pieces. The armature 64 which is generallyof channel form with the flanges thereof adjacent the pole piecesissecured to a sleeve 66 journaled on a stationary shaft 68 supported bybrackets 70 and 72 on the'base plate 10.

A spiral spring 74 having its inner end secured to the sleeve 66 and itsouter end secured to the bracket 70 :is adapted to urge the armature 64out from between the pole pieces 60 and 62 and the extent of movement ofthe armature is'limited by the provision of an arcuate slot 76 in thearmature and a closely wound helicalspring 78 having one end secured tothe bracket 70 with the other end located within the slot 76. Thisspring 78 also acts as a buffer to cushion the motion of the armature atboth ends of its movement as it is oscillated about the pivot shaft 68beingmoved in one direction by the spring 74 and in the other directionby magnetic action when the electromagnet is energized by the timingmechanism.

A driving pawl in the form of a hairpin spring or spring wire of U-shapeindicated generally at 80 is secured to the sleeve 66. As shown in Fig.4, this spring is formed with substantially parallel arms of unequallength connected by several turns or coils to provide the desired springaction. The spring 80 is arranged with these arms extendingsubstantially parallel to the axis of the shaft 63 with the shorter arm82 tightly secured to the sleeve 66 between similarly formed sheet metalplates 84 and 86 which are clamped around the sleeve and welded orriveted together. The abutting flat portions of the plates 34 and 36 atone side of the sleeve 66 are provided with similarly formed spacedextensions 38 and 90, respectively, which are offset outwardly from theplanes of the flat portions to form longitudinally aligned groovesbetween these extensions to receive the longer arm 92 of the spring 80.

The free end of the arm )2 projects beyond the extensions 38 and 9 0 toengage a ratchet wheel 94 and arm 92 acts as a spring pawl to advancethe ratchet wheel one tooth each time the electromagnet is energized andthe armature 6 1 moved in one direction. The end of arm 92 is held bythe spring action of the coils of the hairpin'spring in engagement withthe ratchet wheel and the grooves between plates 84 and 86 which receivearm 92 function as guides for the radial movement of the arm withreference to the axis of the shaft 68 as the end of the arm is radiallydisplaced by the teeth of the ratchet wheel.

The ratchet wheel 94 is secured to a driving worm 96 journaled on thestationary shaft 66 and the driving worm carries an index or star wheel93. A detent spring 100 which is secured at one end to the bridge 16 asby screws 102 has its free end of substantially V-shape to engage theteeth of the star wheel to prevent reverse rotation or any movement ofthe ratchet wheel and driving worm at times other than when these partsare being moved in one direction by the spring pawl.

The driving worm 96 engages a gear 104 secured on a shaft 106 mounted inbrackets 108 and 111) on the base plate 10, and a worm 112 on shaft 106meshes with a gear 114 which is rotatable on a central shaft 116 andforced by a spring 118 into frictional driving engagement with a collar120 fixed to the shaft. The shaft 116 is journaled at one end in thebridge 16 and extends through the base plate and a dial plate 122 withthe usual minute hand 124 mounted on the end of this shaft and the hourhand 126 driven thereby through a reduction gear train consisting of thegears 12%, 139, 132 and 134.

A setting mechanism for manually setting the position of the handsincludes a setting stem 136 which is journaled for rotation and limitedendwise movement in a mounting plate or other support 13% and a bracket140 secured to the plate 138 with the stem extending through the dialplate 122 and provided with a knurled knob 142. A gear 144 and a metaldisk 146 of slightly larger diameter than the gear are secured on thestem 136 which is normally held against endwise movement with the disk146 in engagement with plate 138 by means of a spring 148. An idler gear150 is mounted on the plate 138 in mesh with the gear 130 of thereduction gear train and this gear 150 is adapted to be engaged by thegear 144 on the setting stem when the stem is moved endwise to thenprovide for the adjustment of the hands by rotation of the stem in theusual manner.

As shown in Figs. 6 and 7, a spring contact arm 152 is secured to andinsulated from the base plate 10 and formed with a flanged end whichextends over the edge of the disk 146 on the setting stem 136 and isnormally spaced therefrom but will be engaged thereby when the stem 13-6is moved endwise during the setting operation to complete a startingcircuit to be hereinafter described.

The base plate 3.11 may be secured by screws 154 to the mounting plateor other support 138 and a sheet metal cover 156 secured as by screws onposts 158 and 160 on the base plate 16 to conceal and protect the timingand driving mechanisms.

Referring now to the diagrammatic showing in Fig. 8 the electromagnet isprovided with two windings as indicated at 162 and 164. Although shownas separated these windings are wound in bifilar relationship, or inother words, the two wires constituting these windings are parallel andwound simultaneously on the core 54 with the same number of turns. Thesource of current, indicated as a battery 166, is connected directly toone end of each of the windings 162 and 164 by conductor 168.

The winding 162 which may be termed the running winding is connected atits other end by conductor to the contact blade 50 through the spring 46and the running circuit will therefore be'completed whenever the contact40 on balance wheel armature 20 is in engagement with the contact blade50 through the balance staff 22 and hairspring 26 to ground.

The ends of the winding 164 are connected together, thus shortcircuitingthis winding on itself to function as a magnetic damping means, and thewinding 164 is tapped at an intermediate point which is electrically oflcenter with this tap connected by conductor 172 to the contact arm 152to thereby function as a starting winding when a circuit is completedthrough the disk 146 and setting stem 136 to ground.

In Fig. 8 the relative locations of the several parts have beendiagrammatically shown when the circuits are open and the balance wheelarmature 20 is in the position of rest or equilibrium to which it isurged by the hairspring 26. In this position it will be seen that thecontact 40 is slightly spaced from the contact blade 50 and the contactarm 152 is also spaced from the disk 146. When the setting stem 136 ismoved endwise during the setting operation the disk 146 will engage arm152 to complete a starting circuit which will be effective, since theconnection of conductor 172 to the winding 164 is electrically offcenter, to create a magnetic field through the pole pieces 56 and 58 toattract the balance armature 20 and rotate the armature in a clockwisedirection, until the arms of the armature which were closest to the polepieces are drawn to substantially the position shown in Fig. 2.

The armature will then be magnetically held in this position duringrotation of the setting stem to set the hands but as soon as the stem isreleased and returned endwise by the spring 143, the starting circuitwill be broken at contact arm 152 and the armature will then be rotatedin a counter-clockwise direction with suflicient inertia to engagecontact 40 thereon with the contact blade 50 and move on past thisblade.

it will be understood that whenever contact 40 engages the contact blade50 a circuit will be completed through the running winding 162 and thebalance wheel armature will be sustained in oscillation, after starting,by magnetic impulses imparted thereto upon cnergization of this windingduring movement of the armature in both directions. Whenever the winding162 is energized, a current will also be set up or induced in theshort-circuited winding 164 which will thereby function as a magneticdamping means to practically eliminate all sparking at the contact 40and contact blade 50.

In an electric clock of the magnetic impulse type for use in automobilesit is desirable to provide some means to compensate for the widevariations in battery voltage such as affect the rate of the clock bychanging the magnetic field strength which varies the amplitude of thebalance. The eflfect of varying voltages would be even more pronouncedin the present clock wherein, as distinguished from prior clocks of thistype, there is no mechanical connection between the timing mechanism andthe driving mechanism so that there is no restraint such as caused bythe drive and gear train friction on the amplitude of the balance wheelarmature.

The provision in the present clock of separate pole pieces for theindependent armatures of the timing mechanism and the driving mechanismis employed in the manner to be now described to maintain the magneticflux utilized to operate the balance wheel armature at a practicallyconstant value throughout the range of voltage variations that areencountered in automobile operation.

With reference first to the magnetic circuit of the timing mechanism,the electromagnet core 54, the pole pieces 56 and 58, and the balancewheel armature 20 are made from a material such as a nickel iron alloycontaining over 40% nickel, and preferably a 50% nickel iron alloy,which will become magnetically saturated at very low magnetic densitiesor under a very low magnetizing force.

The amount of flux, except for leakage, which is capable of passingthrough this magnetic circuit is determined and limited in the presentarrangement by the minimum cross-sectional area of the pole pieces 56and 58 which are formed with their smallest cross section at the poletips, and the magnetic circuit is so designed that the application of arelatively low voltage to the running winding 162 of the electromagnetwill produce a magnetizing force sufiicient to substantially saturatethe pole pieces 56 and 58. The cross section of the narrowest portion ofthe armature 20 is larger than that of the pole pieces or pole tips sothat the armature itself will not be substantially saturated but theflux which operates the armature will be kept practically constant atvarying voltages by reason of the saturation of the pole pieces.

At higher voltages than the minimum necessary to saturate the polepieces or the reduced tips thereof, there would ordinarily be magneticleakage through the air gaps in the magnetic circuit and some of thisleakage flux would tend to increase the total flux acting on theunsaturated armature and increase its amplitude.

To absorb this leakage flux in addition to any flux in excess of thatnecessary to saturate the pole pieces 56 and 58, the magnetic circuitthrough the pole pieces 60 and 62 for the driving armature 64 has beendesigned to function as a shunt path. For this purpose, the pole pieces60 and 62 are made from a material such as Armco iron or Swedish iron orother known magnetic materials which do not become magneticallysaturated or substantially so at the maximum voltage or magneticstrength encountered in the present application.

Although the principal features of the present clock construction willbe apparent from the foregoing description it is desired to callattention to certain distinguishing features thereof which have beencombined to produce an automobile clock of exceptional performance fromthe standpoint of both accuracy and reliability.

By separating the clock mechanism into mechanically independent timingand driving mechanisms, the gear train friction and any variationstherein will have no effect on the balance wheel timing which controlsthe periodic energization of the electromagnet. The balance wheel timingwill also not be afiected by variations in voltage since the pole piecesfor the balance wheel armature will be substantially saturated at theminimum voltage and the pole pieces for the separate driving armatureconstitute an unsaturated shunt circuit to absorb the excess fluxgenerated at higher voltages.

Destructive sparking at the contact points is effectively prevented bythe provision of the short-circuited damping winding on theelectromagnet and this winding is further employed in a starting circuitwhich includes a starting switch operated by the setting stem formanually setting the position of the hands.

Many other features including the details of construction and themounting of the several parts as disclosed herein are considered to alsoconstitute distinct improve ments over prior practice. It will beunderstood that many modifications and the separate use of certainfeatures are contemplated as coming within the scope of the presentinvention as defined in the claims appended hereto.

We claim:

1. In an electric clock having an electromagnet and means forperiodically energizing said electromagnet, a clock gear train includinga ratchet wheel, and a driving mechanism for said ratchet wheelincluding a pivotally mounted armature, means to oscillate said armaturein response to energization and deenergization of said electromagnet, ahairpin spring having two arms, means securing one arm of said hairpinspring to said armature, said securing means guiding the other arm ofsaid hairpin spring for radial movement with respect to the pivotal axisof said armature, and means maintaining the free end of said arm inyielding engagement with said ratchet wheel.

2. In an electric clock having an electromagnet and means forperiodically energizing said electromagnet, a clock gear train includinga ratchet wheel, and a driving mechanism for said ratchet wheelincluding a pivotally mounted armature, means to oscillate said armaturein response to energization and deenergization of said electromagnet, ahairpin spring having substantially parallel arms connected by severalcoils and extending parallel to the pivotal axis of said armature, andmeans securing one arm of said hairpin spring to said armature, saidsecuring means guiding the other arm of said hairpin spring for radialmovement with respect to said axis with the free end of said arm beingmaintained in yielding engagement with said ratchet wheel by saidseveral coils.

3. In an electric clock having an electromagnet and means forperiodically energizing said electromagnet, a clock gear train includinga ratchet wheel, and a driving mechanism for said ratchet wheelincluding a pivotally mounted sleeve, an armature on said sleeve, meansto oscillate said armature and sleeve in response to energization anddeenergization of said electromagnet, and a spring pawl mounted on saidsleeve to engage said ratchet wheel, said pawl consisting of a hairpinspring having substantially parallel arms, abutting plates securedtogether around said sleeve with one arm of said spring clamped betweensaid plates, and spaced extensions on said plates to receive the otherarm of said spring which is extended to yieldingly engage said ratchetwheel and permit radial movement of said arm with respect to the sleeve.

References Cited in the file of this patent UNITED STATES PATENTS381,856 Sibley Apr. 24, 1888 1,821,100 Larrabee Sept. 1, 1931 1,911,062Conrad May 23, 1933 1,965,763 Battegay July 10, 1934 2,266,015 Fink Dec.16, 1941 2,590,365 Anderson Mar. 25, 1952 FOREIGN PATENTS 855,412 FranceFeb. 12, 1940 504,553 Great Britain Apr. 27, 1939 78,486 Sweden Sept.26, 1933

